I think this is true, but its inconsistent (at least from a probability standpoint) with the kind of rigorous EENS you hold to.
It seems *highly* implausible that there are no souls among the Eastern Orthodox, the Protestants, even non Christian religions, who ultimately, at the end of the day, *would* want Catholicism if they knew it was true and what God wanted.
Granted, I suppose you could fall back on "well we just can't try to fully understand God" but I suspect this may have been why Lefebvre thought as he did about EENS.
If some among these groups don't attain to true supernatural faith, it's because they didn't really want supernatural faith. So if they do not receive the Beatific Vision, it's because they didn't really want it. As I've told you before, though, I don't believe that everyone in hell suffers the same, and some probably suffer very little ... if they lived naturally virtuous lives. So, at the end of the day, everyone receives what they sought and what they wanted. Seek and ye shall find, promised Our Lord. If they truly sought it, they would receive.
This has nothing to do with EENS whatsoever other than your presupposition that there are some among non-Catholics who did truly want supernatural faith. Your perception of soteriology is an extremely naturalist, almost Pelagian one, where you assume that some kind natural desire or natural virtue translates automatically to the supernatural.